Diaphragm



Feb. 26, 1924. 1,484,821

H. DUNCAN DIAPHRAGM Filed April 2, 1919 phragms for acousticinstruments, f'such as" Patented Feb.- 26, i 1924.

mast I princely,- or MAnw n 'NEw' JERSEY} DIAPHQAGM.

i Application filed April 2,1919; Serial nb 2a'e,9sa

Tohll whomz't y concern: 1 I

Be it known that IfHAItRY L." DUNOAN,' a citizen of the'UnitedStfltes,and resident of Mahwah,county of Bergen, State "Of: New ,Tcrsejghavemade a certain new and useful: Invention Relating to .Dia'phragiris, of;which the following va specificat-ion'itaken in connection with theaccompanying draw- 11g 1 I z This invention relates "especially v diaphonographs, telephones,*-et c., in which the diaphragm is preferablyformed of.-fibrous material, su'chjas the I desired f'nurnber ofthicknesses of o suitable cotton jcloth, strong blotting ap r,c'ottonlfibatting, 'et'c.,' --carry,-,

ing and preferably 'quite thoroughly: im pregnated with 'cured phenoliccondensation cementing material, such as 'balrelit-e', coin densite."or: Redmanol varnish compositions;

" Various parts of 'th'e diaphragniflmay" be' 'stiflenedi to thedesired-extent by 'ior-I'nin'g corrugation-s or "coned up. or archedprom-,-

a nite degreeof peripheral elongation. Such- =ofsubstantially uni-fornqstrength in each I directionand in whichthe threads are pref- -tio1is,thereinand at'the same time .the' edge portions "of the diaphragmmay-"be given a' wavyor fluted form so as to Secure a' defi a diaphragmwhen clamped or 'I'nounted' 'so that this inorenr "'le'ssirregularorwavy,

edgeis forced to a greater extent into flat purpose, the cot-ton threadsunder such conf ditions after the materialhas been impregatedso as tocontaindforty to sixty per.

or straightposition is thereby placed under "radial tension in itsinnerporti'qns because. this flattening-tends to increase the-- edgediameterof the diaphragnil One or "more layers of "such. fabricor-"fibrous material ,m'aybe unitedby the incorporated curedphen'oliccondensation cementing material v 7 portions or corrugatedor ,otherwarpedflor 7 so as to '.form;anj elastic :rigid and strong diaphragmmaterial whichis especially ad'f vantageou's for such tensioning wavy,ed'ge construction," "'sin-ce th'e desireddefinite" pei I riphera'l.elongation may; be simply and ef-' fectivel'y secured therein bypressure mold.-

-. :ing operations in; suitable-dies when the in asoinewhatdiagrammaticv way. anumber heatjciiringof the material is -efl'ectedi Inthe" accompanying dr ajwingf showing of illustrative embodiments of thisinven-}' tion, U H .7

" this charact'en-partly in section. i'

Fig. 2 is a diagrammatic-sectional' view' showing the'inounting of sucha diaphrag n;

Fig 1" is aside viewjof aidia'p hragn sure molding and curing action is'usually should also-have sufliciently long fibre v t0 about 300 to.320Fahrenheit for fifteen to thirty minutes or so; although by using 1i a.longertime the curing :heat'may be. con-" j' siderably reduced. gThefibrous n aterial"7 0 4 give the desired strength and coherence dur-iing" the pressureficuring or molding o ra- ,ci'on whereconsiderabledistortiono jthe' previously forrned sheet orblanketfibrous- ,1 I longer fibre gives greater strength the materialoccurs at this time and ofj cou-rse' finished article; although thecementing ac- Y tion' of the .bakelite Or other phenolic 'condensationcementingmat'eriaI naturally cures. the fibres together and gives themgreatly increased strength under these conditions. For many purposesclosely, woven cotton "fabricof which the threads are preferably as i.

erfably loosely twisted is desirable "forfthis cent more or less ofdried'bakelitevarnish "No, 1, for example, yielding suflieiently -un-.der the heat curing'treatn ent to permit con- 0siderab-lei-dist'ortion-so'that-the wavy edge .1

distorted portions oft'he diaphragm can be --'reliably produced,andfrelativelyjconstant shape'ystrength and other properties-secured iwhen "the. same number. of thicknesses of: "similarly; impregnated"fabric are *used' in each case. As an illustrative exampleslnallphonograph.diaphragmstwoorthreeiinchesv m diameter'may'jbe convenientlyformed of 'three or four layers of light muslin-earry v j .Jingaboutfifty per cent. of cured bakelite varnish-andgiinited under'such' highfpres '105z 'sure curing conditions as above described so as to. havea'thicknessof some .six to twelve thousandthsof an inch. Under some Iconditions,-however,asmaller number or. p cottonbatting may us d withquite-good results. "For larger 'diaphra'gms of six' layers of thickerwoven fabric; paper .or

ice 7 inches or more in diameter heavier fabric or other material may,of course, be used or a greater number of layers of the lighter materialmay be employed, and in such cases a greater number of edge flutes mayusually be employed to advantage for such radial tensioning purposes ascompared to the relatively small diaphragms two or three inches indiameter where four to six flutes more or less are more convenient anddesirable for most purposes.

As indicated in Fig. 1 the diaphragm 1 may be formed of a number oflayers of cotton or other suitable fabric carrying and preferablythoroughly incorporated with such phenolic condensation cementingmaterial as dried bakelite varnish compositions. Several layers of twoounce cotton fabric of this character carrying about fifty per cent byweight ofrsuch cementing material may be assembled in a suitable moldand forced together under pressure of a number of hundred pounds persquare inch, preferably in accurately shaped or equalizing moldspreventing excessive local pressures so that the fibrous material is notdestroyed or distorted locally to an undesirable extent; During thisheat curing and molding of the diaphragm 1 the edge portions 4 arepreferably given a wavy or fluted form, three to six high spots such as4 being formed therein with a corresponding number of intermediate lowspots. A sinusoidal wavy form is desirable for this fluted or wavy edgewhich may of course merge into the relatively flat portion of thediaphragm within at any suitable point, although it is not necessary inall cases for the wavy or transversely distorted portions to extend morethan about a third of the way to the center of the diaphragm. In somecases it is desirable to reenforce and strengthen this wavy edge portionby incorporating therewith additional impregnated fibrous materialduring the heat curing and molding of the diaphragm and as shown in Fig.1 an edge tensioning ring 5 may be used composed of additionalthicknesses of impregnated cloth, paper or other fibrous material whichmay be arranged on one or both sides of the other layers or interposedbetween them so that under the heat curing treatment they becomesecurely cemented and united to the edge portions of the diaphragmsheets or layers so as to proportionately strengthen this wavytensioning edge portion.

When used such a diaphragm may advantageously be yieldingly clamped ormounted between any suitable form of elastic or yielding clampinsupporting surfaces, such as circular or flat sectioned rings or gasketsof vulcanized rubber, soft paper or the like, and Fig. 2 showsdiagrammatically a suitable arrangement for this purpose in which theclamping supporting means may comprisea rigid clamping ring or member 6provided with a recess having an internal shoulder or flange 8 againstwhich the rubber ring or yielding clamping member 9 may abut on itsinner side, while at the same time sufficient free space is provided inthe clamping means outside of this rubber ring, so that its free outwardexpansion can take lace during the clamping of the diaphragm.

he clamping members 6, 7 of brass or other suitable material may thussupport the soft and yielding elastic vulcanized rubber clamping ringsor members 9 which prefer ably have somewhat rounded contact surfacesfor engagement with the diaphragm edge, such contact surfaces beingadvanta-' geously located toward the outer edge of these yieldingclamping rings or members so that the initial contact occurs at thispoint and a considerable radial tensioning may thus be secured on anydiaphragm through the outward radial expansion of the clamping ringscaused by their transverse compression, even aside from the radialtensioning secured by the flattening of the wavy edge portions of such aspecially shaped diaphragm as described. In the mounting the elasticclamping rings or members may be forced together as by screws 10 so asto engage the diaphragm on each side throughout its entire peripherywhich is of course desirable and subsequent pressure yieldingly forcesthe wavy diaphragm edge into relatively flat position, thus tending toincrease the diameter of this edge portion of the diaphragm andsimultaneously exert radial tension on the inner portions which isdesirable for many purposes because securing increased pitch and morereliable vibration in response to various impulses.

Fig. 3 shows another form of diaphragm in which not only the activevibrating portion is of substantially uniform thickness throughout, butin which the edge portion may also be of substantially the samethickness and such a diaphragm may be formed of the desired number oflayers of such coated or impregnated cloth or other fabric or fibrousmaterial. The different parts of the diaphragm may under such conditionsbe stiffened or strengthened by appropriately shaping them, the center 3of this diaphragm 1 being coned up or projecting from the plane of thediaphragm body to a progressively increasing extent which gives greatlyincreased stiffness thereto and promotes the vibration of this part ofthe diaphragm as a unit by minimizing local bending distortion thereof.A uniform thickness edge portion of a wavy character may beadvantageously formed on such a diaphragm. As indicated the high spots12 may be sufiioiently distorted as compared to the low spots 13 tosecure a considerable definite increased peripheral length so as toexert a desirable radial tensionin action when these wavy edge portionsare attened. For some purposes it is desirable to form any suitabletransversely extending stiffened portion such as the integral stiffeningrib or corrugation 11 between such a wavy edge portion and the innerportions of diaphragms of these types. Such a stiffener or rib may havesufficient stiffness transverse to the plane of the diaphragm tominimize or prevent undesirable buckling displacement of thepartswithin, which may be radially tensioned by the edge portionsthrough the curved connections shown in connection with the rib. Such adiaphragm may be molded in suitable shaped molds under high pressure soas to compact the fibrous material and quite thoroughly shape it to thecontour of the mold at the same time that the phenolic condensationcementing material is cured or solidified into its strong solidcondition in which it gives such a high degree of resilient strength tothe incorporated cotton or other suitable fibrous material.

Fig. 4 shows another form of diaphragm which may be advantageouslyproduced from such fibrous material, the projecting stiffened centerportion 3 being coned up gradually as indicated so as to project beyondthe diaphragm body 1 and the edge portions may be given a tensioningaction by forming three to six flutes or waves therein having high spots15 and interposed low spots 14, the planes of which may be a sixteentli.to an eighth of an inch or so apart in the case of relative] small diahragms two or three inches in iameter. ig. 5 shows another form ofdiaphragm which may be made of such material and have four to six ormore edge flutes or wavy portions, such as 14, 15, connected with asuitably reenforced or stiffened diaphragm center of any desiredcharacter. If desired such a stiffened center may comprise a series ofcorrugations 17, 18, 19, the center 16 being flat,

, if desired, and stiffened in other ways under tion cementing material.

some conditions.

Fig. 6 shows still another form of diaphragm which may be advantageouslyformed of such fibrous material'carrying or impregnated with curedphenolic condensa- The diaphragm may have fluted or wavy edge portions,if

desired, and may comprise a series of high spots or portions 24 andcorrespondingly displaced intermediate low portions 26, and if desiredalso this wavy edge portion may be reenforced by an additional amount ofsimilar impregnated fibrous material, such as the incorporated or unitededge tensioning ring 25 which may have several times as great thicknessas the inner portions ofthe diaphragm which may be of substantiallyuniform thickness, of say, five to ten thousandths of an inch in smalldiaphragms, for example. This diaphragm may have a stiffened centralportion comprising a series of corrugations which may be of such form orless conically inclined portions between corrugations or projections,such as 31, 32, 43 and 44 may be progressively flatter so as to more orless gradually approach the plane of the diaphragm outside which gives adesirable arrangement having a stiffening action which may approximatesuch a coned up shape as shown in Fig. 4, if desired.

Fig. 7 shows another form of diaphragm in which, if desired, thediaphragm center 33 may be coned up or stiffened and may havesubstantially the same thickness as the diaphragm body 34. In some casesit is desirable to unite or mold a metallic edge tensioning ring intosuch a diaphragm and for this purpose a fiat or wavy tensioning ring 36which preferably has a much greater radial width than its thickness maybe united to the edge portions of the impregnated fibrous diaphragmmaterial in any suitable way. These edge portions 35 of cloth or papermay in some cases be more or less brought around the metallic tensioningring 36 so that the enclosing portions 37 are formed thereon which maybe securely united to the diaphragm body 34 and to the tensioning ringduring the pressure heat molding operation. If desired, however, themetallic edge tensioning ring may be interposed between the differentlayers of impregnated or coated fabric which may be forced around thering during the heat moldin so as to secure effective union between51888 parts. This molding operation may also in some cases serve to givethe diaphragm edge portions a wavy or fluted contour similar to that ofthe tensioning rin although the tensioning ring if not uncfuly stiff maybe fluted at the same time that it is enclosed within or united to thefibrous diaphragm material. Such a metallic tensioning ring is desirablefor relatively large diaphragms in some cases, although of coursetemperature expansion is much better equalized when the edge tensioningring or portion is formed of practically or identically the samematerial as the inner portions or body of the diaphragm.

This invention has been disclosed in con: nection with a number ofillustrative embodiments, forms, proportions, elements.

. ditions, and methods of preparation, pro

parts, shapes, materials, compositions, conmember formed in saiddiaphragm adjacent its edge portion and joined to its central portionbya curved connection portion.

2. The integral acoustic diaphragm, the central portion ofSaiddiaphragm'being stiffened, the'edge portions of said diaphragm beinggiven a Wavy form to secure increased' peripheral elongation and atransversely extending intermediate stiffening member having a portionextending sub stantially perpendicularly to the plane of the diaphragmand formed in said diaphragm adjacent its edge portion and joined to itscentral portion by a curved connection portion.

3. The acoustic diaphragm, the edge portions of said diaphragm beinggivena Wavy form to secure increased peripheral elongadiate stiffeningmember havinga-portion extion and a transversely extendingintermetending substantially perpendicularlyto the plane ofthe-diaphragm and formed'in said diaphragm inside of andclosely adjacentits edge portion.

4:. The acoustic diaphragm-,theedgep'ortions of said diaphragm beinggiven awavy form to secure increased peripheral elongation and atransversely extending'interme diate stiffening member formed in"saiddiaphragm. inside of and closely adjacent its edge portion.

5. The one piece acoustic diaphragm, the edge portions of 'saiddiaphragm being adapted to exert a radial tensioning action on thecentral portions and a transversely extending intermediate stiffening,member formed in said diaphragm inside of and adjacent its edge portion,said stiffening member having a portion-extending in adirec tionsubstantially perpendicular to the plane of the diaphragm.

6. The acoustic diaphragm, the edge portions ofsaid diaphragm beingadapted to exert a radial tensioning action on'the'central portions and-a transversely extending intermediate stiffening member formed in' saiddiaphragm inside of and adjacent its edge portion: HARRY L. DUNCAN;

